Packages

As your projects grow, a single file isn't enough. You need folders to organize your code! A package is simply a folder containing Python modules. Packages let you build large applications with clean, hierarchical organization.

What is a Package?

                    Package Structure                             

                                                                  
   my_package/                    ← Package (folder)             
    __init__.py               ← Makes it a package            
    module_a.py               ← Module                        
    module_b.py               ← Module                        
    subpackage/               ← Subpackage (nested folder)    
        __init__.py           ← Makes subpackage              
        module_c.py           ← Module in subpackage          
                                                                  

Creating a Package

Step 1: Create the Directory Structure

myproject/
 mypackage/
    __init__.py
    math_utils.py
    string_utils.py
 main.py

Step 2: Add Modules

# mypackage/math_utils.py
def add(a, b):
    return a + b

def multiply(a, b):
    return a * b

# mypackage/string_utils.py
def reverse(text):
    return text[::-1]

def uppercase(text):
    return text.upper()

Step 3: Create init.py

# mypackage/__init__.py
"""My utility package."""

from .math_utils import add, multiply
from .string_utils import reverse, uppercase

__all__ = ['add', 'multiply', 'reverse', 'uppercase']

Step 4: Use the Package

# main.py
from mypackage import add, reverse
# Or
import mypackage
result = mypackage.add(2, 3)

The init.py File

This special file:

• Makes a directory a package
• Runs when the package is imported
• Can be empty or contain initialization code

# mypackage/__init__.py

# 1. Import submodules for easier access
from .math_utils import add
from .string_utils import reverse

# 2. Define package-level variables
VERSION = "1.0.0"

# 3. Control what 'from package import *' exports
__all__ = ['add', 'reverse', 'VERSION']

Key Takeaways

                   Remember These Points                          

                                                                  
   Package = folder with __init__.py                           
                                                                  
   __init__.py makes directory a package                       
     Can be empty or contain initialization                       
                                                                  
   Use dot notation for imports                                
     from package.module import function                          
                                                                  
   Subpackages are packages inside packages                    
                                                                  
   __all__ controls 'from package import *'